Patent Document 1 discloses a piezoelectric resonator including: a piezoelectric resonator plate provided with excitation electrodes; a support frame disposed so as to surround the piezoelectric resonator plate; and coupling parts that couple the piezoelectric resonator plate to the support frame. In this piezoelectric resonator, the coupling parts are constituted by a first coupling part and a second coupling part each connecting a corresponding corner of the vibrating part respectively to different corners of the support frame in the −X direction. An end of the piezoelectric resonator plate in the −X direction is supported by the support frame in a cantilevered manner.
Patent Documents 2 and 3 are known as inventions related to an AT-cut crystal resonator whose main vibration mode is a thickness shear vibration. The At-cut crystal resonator is suitable for downsizing and increasing the frequency and has excellent frequency temperature characteristics.
When the crystal axes of a synthetic crystal are respectively referred to as an X axis, a Y axis and a Z axis, an AT-cut crystal resonator is obtained by rotating the synthetic crystal about the X axis by 35° 15′. Note that, in the present description, the Y axis after rotated by 35° 15′ is referred to as a Y′ axis, and the Z axis after rotated by 35° 15′ is referred to as a Z′ axis.
Patent Document 2 discloses a crystal resonator 100 including: a vibrating part 300 that is provided with excitation electrodes 200; a frame part 500 surrounding the vibrating part 300; and connecting parts 400 that connect the frame part 500 to the vibrating part 300. In this crystal resonator 100, the connecting parts 400 are connected to the frame part 500 at three positions (each corner parts and a central part) on one end side (i.e. at six positions on both end sides) of the vibrating part 300 in the X axis direction of the crystal axes (see FIG. 15).
Also, Patent Document 3 discloses a piezoelectric resonator plate including: a vibrating part having main surfaces on which excitation electrodes are respectively formed; a frame part arranged on an outer circumferential side of the vibrating part via a through groove; and support parts connecting the vibrating part to the frame part. Sawtooth notches are formed on a front side and a rear side of each respective support part along its width direction.